linux-kernel - Re: [PATCH] x86/cpuid: expose AVX512_4VNNIW and AVX512

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Date:   Fri, 28 Oct 2016 14:07:21 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Luc, Piotr" <Piotr.Luc@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "he.chen@...ux.intel.com" <he.chen@...ux.intel.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "Kang, Luwei" <luwei.kang@...el.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>
Subject: Re: [PATCH] x86/cpuid: expose AVX512_4VNNIW and AVX512_4FMAPS
 features to kvm guest



On 28/10/2016 13:08, Borislav Petkov wrote:
> On Fri, Oct 28, 2016 at 12:17:02PM +0200, Paolo Bonzini wrote:
>> Otherwise, if you add a cpuid_count_edx function to processor.h then one
>> can do:
>>
>> 	entry_>edx &= cpuid_count_edx(7, 0);
>>
>> which is decent too.
> 
> If you think of iterating over the cpuid_bits[] array and recreating the
> CPUID leaf for KVM, sure, why not...
> 

cpuid_count_edx would be just

static inline unsigned int cpuid_count_edx(unsigned op, unsigned count)
{
        unsigned int eax, ebx, ecx, edx;

        cpuid_count(op, count, &eax, &ebx, &ecx, &edx);

        return edx;
}

Paolo